A circlip or snap-ring is a substantially circular or annular retaining device having a break or opening which divides the ring into two interconnected curvilinear members. The members may be deflected or flexed to facilitate insertion into a mating groove. Snap-rings are typically formed, stamped, or otherwise constructed from a relatively thin layer of metal which directs a retaining or clamping force along the circumference or periphery of the snap-clip when properly inserted into the groove. The directional force is most commonly used to retain or clamp together various mating components.
The force vector imparted by the snap-ring varies with the type or style of snap-ring that is used and the location of the ring relative to the parts retained or mated. Two main styles of snap-ring are available: an internal snap-ring positioned within a mating internal groove and used for applying outwardly-directed clamping force, and an outer snap-ring positioned within a mating external groove for applying inwardly-directed clamping force. Of these two main types of snap-ring, internal snap-rings are of particular beneficial use within an automatic vehicle transmission.
With an internal snap-ring, the ring is compressed or contracted by deflecting the curvilinear beams or members of the ring and then inserted or “snapped” into a continuous groove cut into an inner circumferential surface of a drum, shaft, cylinder, or other component having an approximately circular cross section. Once inserted into the groove, the snap-ring is then released or retracted into its installed position, directing circumferential clamping force along the groove wall within the relatively restricted space of the groove. In this manner a snap-ring may restrict or minimize any undesirable lateral or axial motion between two or more mating parts, such as within a flange or flanges of a clutch hub and a mating drum within a transmission clutch assembly.
The insertion and removal of a snap-ring during the transmission assembly or build process may be relatively time or material intensive due to the difficulty of accessing various confined areas within the housing. For instance, a person installing a snap-ring must often insert or place the ring into an area having limited accessibility or installation clearance, while simultaneously exerting a substantial amount of force on the curvilinear beams of the snap-ring in order to open or close the ring. The space and force limitations may be considerable enough to necessitate the use of special-purpose capital equipment, potentially adding substantial cost to the assembly process. Additionally, the requisite strength or rigidity for higher-load applications may require a snap-ring formed from a proportionately thicker layer of material, which in turn may lead to an undesirable increase in overall axial space within a transmission case or other housing, resulting in the need for a larger case and/or the re-arrangement of other components within the system.